Heavy-duty vehicles typically include trucks, tractors and trailers. Tractors often pull at least one trailer, and sometimes two or three trailers. The heavy-duty vehicles have axle/suspension systems with at least one transversely extending axle. A brake system, such as an air disc brake system, is associated with the axle/suspension system. The air disc brake system has a brake assembly mounted on each respective end of the axle. Each brake assembly typically includes a carrier, a caliper, a rotor and a pair of disc brake pads.
The heavy-duty vehicle also has multiple tire and wheel assemblies. Each tire and wheel assembly is also mounted on a respective end of the axle. The tire and wheel assembly generally surrounds the brake assembly and, thereby, limits or prevents easy access to the brake assembly for inspection and servicing.
The rotor and disc brake pads are subject to wear during the operation of the heavy-duty vehicle. Vehicle operators, fleet owners, service technicians and enforcement agencies periodically inspect and measure the thicknesses of the rotors and disc brake pads. Such measurements assure that these brake components are within recommended Out-Of-Service limits established by agencies, such as the Commercial Vehicle Safety Alliance (CVSA), or that the brake components require servicing and/or replacement. Obtaining precise and accurate measurements for the thicknesses of the rotor and disc brake pads can be difficult due to the limited access to the brake components when a tire and wheel assembly is mounted on the axle end carrying the brake assembly. It is often necessary to remove the tire and wheel assembly from the axle end to gain sufficient access to the rotor and disc brake pads for inspection and servicing. This can be a labor intensive and time-consuming procedure that takes up service technician time and removes the heavy-duty vehicle from service, thereby reducing the availability of the heavy-duty vehicle.
Previous attempts have been made to enable measurement of rotor and disc brake pads on a heavy-duty vehicle with tire and wheel assemblies mounted and had limited success. For example, one such previous tool has relatively movable jaws that span a rotor to determine a thickness. However, the jaws often engage an outermost area of the rotor that may not be contacted and worn by disc brake pads and, thus, not be a true measure of wear on the rotor. The previous tool has a further disadvantage in that it is generally usable on a limited number of brake assemblies by certain manufacturers because a reference surface used for measurement is machined on the brake caliper or carrier. The previous tools may also not be able to measure both disc brake pads with the tire and wheel assembly mounted on the axle. The previous tool further requires one mechanism to measure a rotor and at least one other mechanism to measure brake pads.
The drawbacks, limitations and disadvantages associated with previously known tools for measuring disc brake component wear make it desirable to improve tools and methods for measuring rotor and brake pad thicknesses. Further, there is generally a limited availability of qualified technicians within a service facility, so anything that can simplify and speed up inspection of brake components is highly desirable. Thus, there is a need for a single tool and method capable of accurately and precisely measuring the thickness of a rotor wear area and of both disc brake pads with the tire and wheel assembly mounted on an axle end of a heavy-duty vehicle regardless of the manufacturer of the brake assembly.